My previous studies have shown that polyamines, either synthesized endogenously or supplied luminally, are required for normal repair of gastric and duodenal mucosal stress erosions and that polyamines accelerate healing at least partly through the process of cell division. The immediate goal of this project is to determine if polyamines exert their effect on cell division by altering the expression of proto- oncogenes during gastrointestinal mucosal healing. To test this hypothesis, three specific aims will be pursued using adult rats: 1) determine, in vivo, the pattern of expression of proto-oncogenes in the process of polyamine-stimulated healing in gastric and duodenal mucosal stress ulcers. I will first examine the expression of the proto-oncogenes c-myc, c-fos, c-jun, jun-B, c-src and c-ras during damage and healing following stress, and then determine the relationship between the expression of proto-oncogenes and polyamines. 2) I will characterize the distribution of cells expressing proto-oncogenes in gastrointestinal mucosa during damage and healing in the stress model using in situ hybridization. These first two specific aims lead logically to the third specific aim addressing the mechanism by which polyamines stimulate the expression of proto-oncogenes during healing: 3) determine the role of proto-oncogene mRNA synthesis, degradation and oncoprotein half-life in the activation of proto-oncogenes by polyamines in vitro. To accomplish these aims, techniques allowing investigation of an animal model in vivo and cultured cells from gastrointestinal mucosa will be employed. The stress ulcer model in rats, cell culture techniques, Northern blot analysis, Western immunoblotting, and measurements of cell or tissue ornithine decarboxylase activity and polyamine levels are used routinely in my laboratory. In preliminary studies, I have demonstrated that gastric mucosal stress ulcers are associated with significant increases in the expression of c-fos and c-myc protooncogenes. This induction of c-fos and c-myc mRNA precedes an increased rate of DNA synthesis after damage and is completely prevented by depletion of polyamines with alpha- difluoromethylornithine (DFMO). These data strongly support my hypothesis and suggest, for the first time, a molecular mechanism for polyamine- stimulated gastrointestinal mucosal healing. Since the current proposal represents a new approach to research into mucosal repair, it will help in identifying the role and the significance of the involvement of polyamines and proto-oncogenes in gastrointestinal mucosal cell renewal.